I'm the sure the OP has his answer (or has moved on since he only has one post) at this point, but since it got bumped...
They are both good entry level kits. (I looked at them both when I was shopping for my e-kit) The Roland has a few 'issues' that you ought to be aware of.
1) The pedals are fixed in placed. If they aren't comfortable to you, you are stuck with it. (also means no double bass play since there isn't an actual kick pad)
2) The module doesn't have a display. Not a big deal unless you want to set the click to a particular speed. You can only guess at what the speed is.
3) There are only 10 predefined 'kits' in the module, none of which can be edited. (The Yamaha has 32 pre-defined kits and 10 slots for custom kits, all of them can be edited using any of the modules 214 built in voices)
4) (very minor) you can't play along with the demo tracks in the brain.
The pluses that the Roland has over the Yamaha are the mesh snare, the samples sound slightly better for some of the kits, the compact size, and an actual 'cymbal' for the hi-hat.
I decided on the Yamaha, myself. I would have gone with Roland if I had been looking at a higher end set, but, IMHO, the DTXplorer is the better kit at that price range. The HD-1 is built to be a beginner kit or a small practice kit, and that is all it will really ever be. You can upgrade the module, but the pedal and pad limitation restrict the amount of usefulness you will get once you start to outgrow it. It's a very good kit if that is what you are looking for, though. The DTXplorer is designed as a beginner kit to get you started while allowing expansion and upgrades as you grow more accomplished. You can upgrade the module, add another pad, replace the single zone pads with multi-zone pads or cymbals, get a double kick pedal, etc... to grow with you as your skills/needs increase.
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Monkey Shines - Blogging my way to being a better drummer.
